I'm pretty crunched for time this morning as Kelsey and I need to head to a doctor's appointment in a minute, so I need to make this brief.
Strength coach Shon Grosse recently came up with a pretty brilliant way to do the one-arm pushup. I'll admit, when I first saw it I thought it was a little "foo-foo," but after trying it a few times myself, I'm sold.

It's much safer on the shoulders than the traditional one-arm pushup, and it's a tremendous challenge for the chest, shoulders, triceps, and core. This is a great option stronger individuals that train with minimal equipment (ex. at home), and/or have exhausted most other pushup variations and are looking for a new challenge:

You can raise/lower the difficulty by adjusting how high the band sits, and by toying with how you hang the band (ex. just one end or both ends hanging from an attachment). For those of you who train at home and have an Iron Gym, that's a perfect place to put the band. Here's mine at home, using a "micro" band from EliteFTS:

Shon gives a fantastic write-up on the entire exercise HERE, so I encourage you to read it if you're looking to give this a shot.